1 //! Contains utility functions to generate suggestions.
2 #![deny(clippy::missing_docs_in_private_items)]
4 use crate::utils::{higher, in_macro_or_desugar, snippet, snippet_opt, snippet_with_macro_callsite};
7 use rustc::lint::{EarlyContext, LateContext, LintContext};
9 use rustc_errors::Applicability;
12 use std::convert::TryInto;
13 use std::fmt::Display;
15 use syntax::parse::token;
16 use syntax::print::pprust::token_to_string;
17 use syntax::source_map::{CharPos, Span};
18 use syntax::util::parser::AssocOp;
19 use syntax_pos::{BytePos, Pos};
21 /// A helper type to build suggestion correctly handling parenthesis.
23 /// An expression that never needs parenthesis such as `1337` or `[0; 42]`.
24 NonParen(Cow<'a, str>),
25 /// An expression that does not fit in other variants.
26 MaybeParen(Cow<'a, str>),
27 /// A binary operator expression, including `as`-casts and explicit type
29 BinOp(AssocOp, Cow<'a, str>),
32 /// Literal constant `1`, for convenience.
33 pub const ONE: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("1"));
35 impl Display for Sugg<'_> {
36 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
38 Sugg::NonParen(ref s) | Sugg::MaybeParen(ref s) | Sugg::BinOp(_, ref s) => s.fmt(f),
43 #[allow(clippy::wrong_self_convention)] // ok, because of the function `as_ty` method
45 /// Prepare a suggestion from an expression.
46 pub fn hir_opt(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<Self> {
47 snippet_opt(cx, expr.span).map(|snippet| {
48 let snippet = Cow::Owned(snippet);
49 Self::hir_from_snippet(expr, snippet)
53 /// Convenience function around `hir_opt` for suggestions with a default
55 pub fn hir(cx: &LateContext<'_, '_>, expr: &hir::Expr, default: &'a str) -> Self {
56 Self::hir_opt(cx, expr).unwrap_or_else(|| Sugg::NonParen(Cow::Borrowed(default)))
59 /// Same as `hir`, but it adapts the applicability level by following rules:
61 /// - Applicability level `Unspecified` will never be changed.
62 /// - If the span is inside a macro, change the applicability level to `MaybeIncorrect`.
63 /// - If the default value is used and the applicability level is `MachineApplicable`, change it
66 pub fn hir_with_applicability(
67 cx: &LateContext<'_, '_>,
70 applicability: &mut Applicability,
72 if *applicability != Applicability::Unspecified && in_macro_or_desugar(expr.span) {
73 *applicability = Applicability::MaybeIncorrect;
75 Self::hir_opt(cx, expr).unwrap_or_else(|| {
76 if *applicability == Applicability::MachineApplicable {
77 *applicability = Applicability::HasPlaceholders;
79 Sugg::NonParen(Cow::Borrowed(default))
83 /// Same as `hir`, but will use the pre expansion span if the `expr` was in a macro.
84 pub fn hir_with_macro_callsite(cx: &LateContext<'_, '_>, expr: &hir::Expr, default: &'a str) -> Self {
85 let snippet = snippet_with_macro_callsite(cx, expr.span, default);
87 Self::hir_from_snippet(expr, snippet)
90 /// Generate a suggestion for an expression with the given snippet. This is used by the `hir_*`
91 /// function variants of `Sugg`, since these use different snippet functions.
92 fn hir_from_snippet(expr: &hir::Expr, snippet: Cow<'a, str>) -> Self {
94 hir::ExprKind::AddrOf(..)
95 | hir::ExprKind::Box(..)
96 | hir::ExprKind::Closure(.., _)
97 | hir::ExprKind::Unary(..)
98 | hir::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
99 hir::ExprKind::Continue(..)
100 | hir::ExprKind::Yield(..)
101 | hir::ExprKind::Array(..)
102 | hir::ExprKind::Block(..)
103 | hir::ExprKind::Break(..)
104 | hir::ExprKind::Call(..)
105 | hir::ExprKind::Field(..)
106 | hir::ExprKind::Index(..)
107 | hir::ExprKind::InlineAsm(..)
108 | hir::ExprKind::Lit(..)
109 | hir::ExprKind::Loop(..)
110 | hir::ExprKind::MethodCall(..)
111 | hir::ExprKind::Path(..)
112 | hir::ExprKind::Repeat(..)
113 | hir::ExprKind::Ret(..)
114 | hir::ExprKind::Struct(..)
115 | hir::ExprKind::Tup(..)
116 | hir::ExprKind::While(..)
117 | hir::ExprKind::DropTemps(_)
118 | hir::ExprKind::Err => Sugg::NonParen(snippet),
119 hir::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
120 hir::ExprKind::AssignOp(op, ..) => Sugg::BinOp(hirbinop2assignop(op), snippet),
121 hir::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(higher::binop(op.node)), snippet),
122 hir::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
123 hir::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
127 /// Prepare a suggestion from an expression.
128 pub fn ast(cx: &EarlyContext<'_>, expr: &ast::Expr, default: &'a str) -> Self {
129 use syntax::ast::RangeLimits;
131 let snippet = snippet(cx, expr.span, default);
134 ast::ExprKind::AddrOf(..)
135 | ast::ExprKind::Box(..)
136 | ast::ExprKind::Closure(..)
137 | ast::ExprKind::If(..)
138 | ast::ExprKind::IfLet(..)
139 | ast::ExprKind::Unary(..)
140 | ast::ExprKind::Match(..) => Sugg::MaybeParen(snippet),
141 ast::ExprKind::Async(..)
142 | ast::ExprKind::Block(..)
143 | ast::ExprKind::Break(..)
144 | ast::ExprKind::Call(..)
145 | ast::ExprKind::Continue(..)
146 | ast::ExprKind::Yield(..)
147 | ast::ExprKind::Field(..)
148 | ast::ExprKind::ForLoop(..)
149 | ast::ExprKind::Index(..)
150 | ast::ExprKind::InlineAsm(..)
151 | ast::ExprKind::Lit(..)
152 | ast::ExprKind::Loop(..)
153 | ast::ExprKind::Mac(..)
154 | ast::ExprKind::MethodCall(..)
155 | ast::ExprKind::Paren(..)
156 | ast::ExprKind::Path(..)
157 | ast::ExprKind::Repeat(..)
158 | ast::ExprKind::Ret(..)
159 | ast::ExprKind::Struct(..)
160 | ast::ExprKind::Try(..)
161 | ast::ExprKind::TryBlock(..)
162 | ast::ExprKind::Tup(..)
163 | ast::ExprKind::Array(..)
164 | ast::ExprKind::While(..)
165 | ast::ExprKind::WhileLet(..)
166 | ast::ExprKind::Await(..)
167 | ast::ExprKind::Err => Sugg::NonParen(snippet),
168 ast::ExprKind::Range(.., RangeLimits::HalfOpen) => Sugg::BinOp(AssocOp::DotDot, snippet),
169 ast::ExprKind::Range(.., RangeLimits::Closed) => Sugg::BinOp(AssocOp::DotDotEq, snippet),
170 ast::ExprKind::Assign(..) => Sugg::BinOp(AssocOp::Assign, snippet),
171 ast::ExprKind::AssignOp(op, ..) => Sugg::BinOp(astbinop2assignop(op), snippet),
172 ast::ExprKind::Binary(op, ..) => Sugg::BinOp(AssocOp::from_ast_binop(op.node), snippet),
173 ast::ExprKind::Cast(..) => Sugg::BinOp(AssocOp::As, snippet),
174 ast::ExprKind::Type(..) => Sugg::BinOp(AssocOp::Colon, snippet),
178 /// Convenience method to create the `<lhs> && <rhs>` suggestion.
179 pub fn and(self, rhs: &Self) -> Sugg<'static> {
180 make_binop(ast::BinOpKind::And, &self, rhs)
183 /// Convenience method to create the `<lhs> & <rhs>` suggestion.
184 pub fn bit_and(self, rhs: &Self) -> Sugg<'static> {
185 make_binop(ast::BinOpKind::BitAnd, &self, rhs)
188 /// Convenience method to create the `<lhs> as <rhs>` suggestion.
189 pub fn as_ty<R: Display>(self, rhs: R) -> Sugg<'static> {
190 make_assoc(AssocOp::As, &self, &Sugg::NonParen(rhs.to_string().into()))
193 /// Convenience method to create the `&<expr>` suggestion.
194 pub fn addr(self) -> Sugg<'static> {
198 /// Convenience method to create the `&mut <expr>` suggestion.
199 pub fn mut_addr(self) -> Sugg<'static> {
200 make_unop("&mut ", self)
203 /// Convenience method to create the `*<expr>` suggestion.
204 pub fn deref(self) -> Sugg<'static> {
208 /// Convenience method to create the `&*<expr>` suggestion. Currently this
209 /// is needed because `sugg.deref().addr()` produces an unnecessary set of
210 /// parentheses around the deref.
211 pub fn addr_deref(self) -> Sugg<'static> {
212 make_unop("&*", self)
215 /// Convenience method to create the `&mut *<expr>` suggestion. Currently
216 /// this is needed because `sugg.deref().mut_addr()` produces an unnecessary
217 /// set of parentheses around the deref.
218 pub fn mut_addr_deref(self) -> Sugg<'static> {
219 make_unop("&mut *", self)
222 /// Convenience method to transform suggestion into a return call
223 pub fn make_return(self) -> Sugg<'static> {
224 Sugg::NonParen(Cow::Owned(format!("return {}", self)))
227 /// Convenience method to transform suggestion into a block
228 /// where the suggestion is a trailing expression
229 pub fn blockify(self) -> Sugg<'static> {
230 Sugg::NonParen(Cow::Owned(format!("{{ {} }}", self)))
233 /// Convenience method to create the `<lhs>..<rhs>` or `<lhs>...<rhs>`
236 pub fn range(self, end: &Self, limit: ast::RangeLimits) -> Sugg<'static> {
238 ast::RangeLimits::HalfOpen => make_assoc(AssocOp::DotDot, &self, end),
239 ast::RangeLimits::Closed => make_assoc(AssocOp::DotDotEq, &self, end),
243 /// Adds parenthesis to any expression that might need them. Suitable to the
244 /// `self` argument of a method call
245 /// (e.g., to build `bar.foo()` or `(1 + 2).foo()`).
246 pub fn maybe_par(self) -> Self {
248 Sugg::NonParen(..) => self,
249 // `(x)` and `(x).y()` both don't need additional parens.
250 Sugg::MaybeParen(sugg) => {
251 if sugg.starts_with('(') && sugg.ends_with(')') {
252 Sugg::MaybeParen(sugg)
254 Sugg::NonParen(format!("({})", sugg).into())
257 Sugg::BinOp(_, sugg) => Sugg::NonParen(format!("({})", sugg).into()),
262 impl<'a, 'b> std::ops::Add<Sugg<'b>> for Sugg<'a> {
263 type Output = Sugg<'static>;
264 fn add(self, rhs: Sugg<'b>) -> Sugg<'static> {
265 make_binop(ast::BinOpKind::Add, &self, &rhs)
269 impl<'a, 'b> std::ops::Sub<Sugg<'b>> for Sugg<'a> {
270 type Output = Sugg<'static>;
271 fn sub(self, rhs: Sugg<'b>) -> Sugg<'static> {
272 make_binop(ast::BinOpKind::Sub, &self, &rhs)
276 impl<'a> std::ops::Not for Sugg<'a> {
277 type Output = Sugg<'static>;
278 fn not(self) -> Sugg<'static> {
283 /// Helper type to display either `foo` or `(foo)`.
284 struct ParenHelper<T> {
285 /// `true` if parentheses are needed.
287 /// The main thing to display.
291 impl<T> ParenHelper<T> {
292 /// Builds a `ParenHelper`.
293 fn new(paren: bool, wrapped: T) -> Self {
294 Self { paren, wrapped }
298 impl<T: Display> Display for ParenHelper<T> {
299 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
301 write!(f, "({})", self.wrapped)
308 /// Builds the string for `<op><expr>` adding parenthesis when necessary.
310 /// For convenience, the operator is taken as a string because all unary
311 /// operators have the same
313 pub fn make_unop(op: &str, expr: Sugg<'_>) -> Sugg<'static> {
314 Sugg::MaybeParen(format!("{}{}", op, expr.maybe_par()).into())
317 /// Builds the string for `<lhs> <op> <rhs>` adding parenthesis when necessary.
319 /// Precedence of shift operator relative to other arithmetic operation is
320 /// often confusing so
321 /// parenthesis will always be added for a mix of these.
322 pub fn make_assoc(op: AssocOp, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
323 /// Returns `true` if the operator is a shift operator `<<` or `>>`.
324 fn is_shift(op: &AssocOp) -> bool {
325 matches!(*op, AssocOp::ShiftLeft | AssocOp::ShiftRight)
328 /// Returns `true` if the operator is a arithmetic operator
329 /// (i.e., `+`, `-`, `*`, `/`, `%`).
330 fn is_arith(op: &AssocOp) -> bool {
333 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide | AssocOp::Modulus
337 /// Returns `true` if the operator `op` needs parenthesis with the operator
338 /// `other` in the direction `dir`.
339 fn needs_paren(op: &AssocOp, other: &AssocOp, dir: Associativity) -> bool {
340 other.precedence() < op.precedence()
341 || (other.precedence() == op.precedence()
342 && ((op != other && associativity(op) != dir)
343 || (op == other && associativity(op) != Associativity::Both)))
344 || is_shift(op) && is_arith(other)
345 || is_shift(other) && is_arith(op)
348 let lhs_paren = if let Sugg::BinOp(ref lop, _) = *lhs {
349 needs_paren(&op, lop, Associativity::Left)
354 let rhs_paren = if let Sugg::BinOp(ref rop, _) = *rhs {
355 needs_paren(&op, rop, Associativity::Right)
360 let lhs = ParenHelper::new(lhs_paren, lhs);
361 let rhs = ParenHelper::new(rhs_paren, rhs);
362 let sugg = match op {
370 | AssocOp::GreaterEqual
379 | AssocOp::ShiftRight
380 | AssocOp::Subtract => format!(
383 op.to_ast_binop().expect("Those are AST ops").to_string(),
386 AssocOp::Assign => format!("{} = {}", lhs, rhs),
387 AssocOp::AssignOp(op) => format!("{} {}= {}", lhs, token_to_string(&token::BinOp(op)), rhs),
388 AssocOp::As => format!("{} as {}", lhs, rhs),
389 AssocOp::DotDot => format!("{}..{}", lhs, rhs),
390 AssocOp::DotDotEq => format!("{}..={}", lhs, rhs),
391 AssocOp::Colon => format!("{}: {}", lhs, rhs),
394 Sugg::BinOp(op, sugg.into())
397 /// Convenience wrapper around `make_assoc` and `AssocOp::from_ast_binop`.
398 pub fn make_binop(op: ast::BinOpKind, lhs: &Sugg<'_>, rhs: &Sugg<'_>) -> Sugg<'static> {
399 make_assoc(AssocOp::from_ast_binop(op), lhs, rhs)
402 #[derive(PartialEq, Eq, Clone, Copy)]
403 /// Operator associativity.
405 /// The operator is both left-associative and right-associative.
407 /// The operator is left-associative.
409 /// The operator is not associative.
411 /// The operator is right-associative.
415 /// Returns the associativity/fixity of an operator. The difference with
416 /// `AssocOp::fixity` is that an operator can be both left and right associative
417 /// (such as `+`: `a + b + c == (a + b) + c == a + (b + c)`.
419 /// Chained `as` and explicit `:` type coercion never need inner parenthesis so
420 /// they are considered
422 fn associativity(op: &AssocOp) -> Associativity {
423 use syntax::util::parser::AssocOp::*;
426 Assign | AssignOp(_) => Associativity::Right,
427 Add | BitAnd | BitOr | BitXor | LAnd | LOr | Multiply | As | Colon => Associativity::Both,
428 Divide | Equal | Greater | GreaterEqual | Less | LessEqual | Modulus | NotEqual | ShiftLeft | ShiftRight
429 | Subtract => Associativity::Left,
430 DotDot | DotDotEq => Associativity::None,
434 /// Converts a `hir::BinOp` to the corresponding assigning binary operator.
435 fn hirbinop2assignop(op: hir::BinOp) -> AssocOp {
436 use syntax::parse::token::BinOpToken::*;
438 AssocOp::AssignOp(match op.node {
439 hir::BinOpKind::Add => Plus,
440 hir::BinOpKind::BitAnd => And,
441 hir::BinOpKind::BitOr => Or,
442 hir::BinOpKind::BitXor => Caret,
443 hir::BinOpKind::Div => Slash,
444 hir::BinOpKind::Mul => Star,
445 hir::BinOpKind::Rem => Percent,
446 hir::BinOpKind::Shl => Shl,
447 hir::BinOpKind::Shr => Shr,
448 hir::BinOpKind::Sub => Minus,
457 | hir::BinOpKind::Or => panic!("This operator does not exist"),
461 /// Converts an `ast::BinOp` to the corresponding assigning binary operator.
462 fn astbinop2assignop(op: ast::BinOp) -> AssocOp {
463 use syntax::ast::BinOpKind::*;
464 use syntax::parse::token::BinOpToken;
466 AssocOp::AssignOp(match op.node {
467 Add => BinOpToken::Plus,
468 BitAnd => BinOpToken::And,
469 BitOr => BinOpToken::Or,
470 BitXor => BinOpToken::Caret,
471 Div => BinOpToken::Slash,
472 Mul => BinOpToken::Star,
473 Rem => BinOpToken::Percent,
474 Shl => BinOpToken::Shl,
475 Shr => BinOpToken::Shr,
476 Sub => BinOpToken::Minus,
477 And | Eq | Ge | Gt | Le | Lt | Ne | Or => panic!("This operator does not exist"),
481 /// Returns the indentation before `span` if there are nothing but `[ \t]`
482 /// before it on its line.
483 fn indentation<'a, T: LintContext<'a>>(cx: &T, span: Span) -> Option<String> {
484 let lo = cx.sess().source_map().lookup_char_pos(span.lo());
485 if let Some(line) = lo.file.get_line(lo.line - 1 /* line numbers in `Loc` are 1-based */) {
486 if let Some((pos, _)) = line.char_indices().find(|&(_, c)| c != ' ' && c != '\t') {
487 // We can mix char and byte positions here because we only consider `[ \t]`.
488 if lo.col == CharPos(pos) {
489 Some(line[..pos].into())
501 /// Convenience extension trait for `DiagnosticBuilder`.
502 pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
503 /// Suggests to add an attribute to an item.
505 /// Correctly handles indentation of the attribute and item.
510 /// db.suggest_item_with_attr(cx, item, "#[derive(Default)]");
512 fn suggest_item_with_attr<D: Display + ?Sized>(
518 applicability: Applicability,
521 /// Suggest to add an item before another.
523 /// The item should not be indented (expect for inner indentation).
528 /// db.suggest_prepend_item(cx, item,
533 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability);
535 /// Suggest to completely remove an item.
537 /// This will remove an item and all following whitespace until the next non-whitespace
538 /// character. This should work correctly if item is on the same indentation level as the
544 /// db.suggest_remove_item(cx, item, "remove this")
546 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability);
549 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
550 fn suggest_item_with_attr<D: Display + ?Sized>(
556 applicability: Applicability,
558 if let Some(indent) = indentation(cx, item) {
559 let span = item.with_hi(item.lo());
561 self.span_suggestion(span, msg, format!("{}\n{}", attr, indent), applicability);
565 fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str, applicability: Applicability) {
566 if let Some(indent) = indentation(cx, item) {
567 let span = item.with_hi(item.lo());
569 let mut first = true;
570 let new_item = new_item
577 format!("{}{}\n", indent, l)
580 .collect::<String>();
582 self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent), applicability);
586 fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str, applicability: Applicability) {
587 let mut remove_span = item;
588 let hi = cx.sess().source_map().next_point(remove_span).hi();
589 let fmpos = cx.sess().source_map().lookup_byte_offset(hi);
591 if let Some(ref src) = fmpos.sf.src {
592 let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
594 if let Some(non_whitespace_offset) = non_whitespace_offset {
595 remove_span = remove_span
596 .with_hi(remove_span.hi() + BytePos(non_whitespace_offset.try_into().expect("offset too large")))
600 self.span_suggestion(remove_span, msg, String::new(), applicability);
607 use std::borrow::Cow;
609 const SUGGESTION: Sugg<'static> = Sugg::NonParen(Cow::Borrowed("function_call()"));
612 fn make_return_transform_sugg_into_a_return_call() {
613 assert_eq!("return function_call()", SUGGESTION.make_return().to_string());
617 fn blockify_transforms_sugg_into_a_block() {
618 assert_eq!("{ function_call() }", SUGGESTION.blockify().to_string());